[BLACKBOX] Illegal Memory Access with Windows 7 - Update 4

From: [at]} <Robert>
Date: Tue, 20 Aug 2013 20:37:05 +0100


The story continues ...

A couple of my colleagues have Windows 7 machines at home, and they have tested
my BlackBox installation on them.

Both machines were able to allocate 1600 MByte, which means that my 800 MByte
limit is some strange interaction with BlackBox
and Windows 7 (both 32-bit & 64-bit) (* as configured by our IT supplier *). I
wonder if I will ever be able to find the cause.

(Remember, a C# .NET test on both these machines could return 1700 MBtye.)


I attach a simpler test program designed to check the available memory, rather
than to stress the garbage collector (in both .pdf & StdCoder formats).


When I run it on XP machines it allocates about 150 10 MByte Blobs.

But when I run it many times it sometimes crashes (usually after about 10 runs,
sometimes after rather more.)

The error is that 'b' is NIL in the "WHILE b.size ...." line of this procedure
called from Kernel.NewBlock.

     PROCEDURE OldBlock (size: INTEGER): FreeBlock; (* size MOD 16 = 0 *)
         VAR b, l: FreeBlock; s, i: INTEGER;
     BEGIN
         IF debug & (watcher # NIL) THEN watcher(3) END;
         s := size - 4;
         i := MIN(N - 1, s DIV 16);
         WHILE (i # N - 1) & (free[i] = sentinel) DO INC(i) END;
         b := free[i]; l := NIL;
         WHILE b.size < s DO l := b; b := b.next END;
         IF b # sentinel THEN
             IF l = NIL THEN free[i] := b.next ELSE l.next := b.next END
         ELSE b := NIL
         END;
         RETURN b
     END OldBlock;


It seems that even with the latest patches discussed there is still a logical
error in the BlackBox allocation code.

I noticed that Helmut Zinn also reported a crash with his tests.


Regards

Robert




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Received on Tue Aug 20 2013 - 21:37:05 UTC

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